Kid stuff is free if your time is worth nothing. There’s always another child outgrowing their car seats and toys and clothes and cribs and games.
The real money goes to:
1) Healthcare (in the US).
2) Childcare or foregone wages.
3) School/housing location (same thing; either tuition, or spending 20+% more for the same amount & quality of house in a nicer school district [and the ongoing cost of servicing the extra mortgage on that]; you can skip this, but if you can at all afford it, you'll not feel like it's optional)
4) Space. Larger housing and larger cars. You can skip this kind of (larger car is less-optional if you have more than three kids) but at significant cost to QOL.